1. Technical Field
The present invention relates to an evaporator structure for a refrigerator-freezer equipped with a defrosting heater, and more particularly to an evaporator structure for a refrigerator-freezer in which the refrigerant tube, heating tube and fins are integrally extruded of a good heat transferring material so that manufacturing process steps are decreased and at the same time cooling efficiency is improved.
2. Prior Art
According to the conventional evaporator structure, various structures have been known in view point that defrosting efficiency is improved so that cooling efficiency is also improved.
As a specific example of that, see the evaporator for a refrigerator-freezer described in Japanese Patent Official Publication Gazette No. Sho-62-39593 as shown in FIG. 1 herein. That apparatus comprises an refrigerant tube 11 bent in zigzag shape, small flat fins 12 inserted to a heater tube which is not shown, and a collar 13. The spacing between the small flat fins 12 is much that the opening at the air inflow side P is larger than air outflow side Q. At the same time the wattage of said heater tube is so made that the air inflow side P is of higher wattage and the air outflow side Q is of lower. There results the advantage that a loss of electric power is prevented. On the other hand, since the manufacturing process is relatively complicated and pitch intervals of the small flat fins 12 are different one another, there has been a worry about decreasing the defrosting efficiency.
If the defrosting efficiency is decreased, air the path is blocked, and therefore the may occur a problem that cooling efficiency is also decreased.
And in addition, a refrigeration system defrosting means is disclosed in U.S. Pat. No. 3,683,636 as shown herein in FIG. 2. In order to improve the defrosting function, a U-shaped defrosting heater 18 has upstanding parallel legs 17a, 17b spaced by a predetermined distance at symmetrical side positions of an evaporator 15. The legs 17a, 17b of the defrosting heater 18 are mounted longitudinally along the length of the evaporator whereby the defrosting heater is simplified and therefore there has been the advantage that the manufacturing cost is decreased. But, since the defrosting heater 18 surrounds the outer periphery of the evaporator, thermal efficiency is decreased, and therefore there has been a worry that defrosting efficiency is decreased.
As another example of conventional technique, an evaporator structure for refrigerator-freezer as shown herein in FIG. 3 is known, and hereinafter it will be briefly described with regard to the structure of said evaporator.
The evaporator structure 10 as shown in FIG. 3 has a refrigerant tube 20 and heating tube 30 (receiving an inserted heater wire 40) are integrally formed. The heating tubes 30 and the refrigerant tubes 20 are symmetrically formed at the top and bottom of a connecting plate. Then, almost the entire area of the plates is cut and pressed out in series to form a plurality of fins 50 spaced apart by predetermined even intervals and arranged in parallel toward one side direction so that air paths 60 are formed.
However, the above-described conventional evaporator structure for a refrigerator-freezer has been had a problem in that the manufacturing process is complicated, and when frost forms, air paths 60 are partially blocked, and the cooled air flow is not smooth so that cooling efficiency is decreased.